Can YOU afford a product recall?

A look at the possible causes and solutions to the contaminated CO2 issues which have dogged the drinks industry in recent times

Danny Smith, ESS.

Over the last few years, there have been many health ‘scares’ concerning contamination in drinks. Public awareness has increased, largely due to the media craving to sensationalise the issues concerned, but it should be noted that in all the health scares, it is pre-packaged drinks that have been at the centre of controversy. It has been these products which have been recalled and disposed of as waste. In effect, this is tantamount to literally tipping vast amounts of money straight into the drain.

The main reason why the packaged drinks industry has suffered more is quite straightforward. Most of the CO2 used in the drinks industry is produced either as a result of fermentation, or as a by-product of another process such as fertiliser production. ‘Fermenter’ CO2 is generally produced by breweries as part of the natural beer brewing process.

It is generally accepted that most breweries recover enough CO2 to satisfy the requirements of their own draught beer production, but there is insufficient gas to satisfy the packaged product demand and CO2 has to be purchased from an outside source to satisfy the requirements. The soft drinks industry relies entirely on gas purchased from outside sources, as there is no natural fermentation process involved, so it is fair to say that the soft drinks industry would, by definition, be at a higher risk level.

CO2 supplied to the drinks industry is derived from many sources and it would be fair to say that the majority of gas supplied would be from a synthesised source. Processes from which CO2 is manufactured include fertiliser production and hydrocarbon fuel manufacture. Both of these processes are very similar in terms of CO2 production and if we look at the key issues it is fairly easy to see why there have been health scares in the past. Fertiliser CO2 comes from a catalytic process; natural gas is fed through a catalytic converter and ammonia is produced. The ammonia is required for the manufacture of ammonium nitrate, ie fertiliser. The other by-product is CO2.

At the output of the catalyst, the CO2 is by no means clean. Compounds that are occurring in the natural gas supply (eg benzene, toluene, hydrocarbons, sulphur compounds) are all present al this stage. The CO2 is then passed through several cleaning stages before being passed as a food grade product. When there has been a ‘benzene’ problem in the past, it can almost certainly be attributed to the fact that one or more of the ‘cleaning’ stages have broken down.

The traditional method of analysis of CO2 has been to take an absorbent tube, concentrate a ‘grab’ sample of gas onto it, and then take it into the laboratory for off-line analysis. It can be proved that this analysis technique can be very ineffective.

Whichever method of CO2 analysis you look at, the gas is produced, by and large, 24 hours per day. The amount of CO2 that is produced during this period can run into numbers of tonnes. A typical grab sample analysis involves a man taking the absorbent tube to the sample point on the stock tank and then concentrating (for example) 2 litres of gas into the tube. A stock tank may contain hundreds of tonnes of CO2 and the contaminants within may not be evenly distributed. (This would become more evident as the tank emptied)

Other analysis methods are similarly flawed. One common practice is to use Tedlar bags and fill them with finished CO2. Apart from the problems highlighted above, there is the additional concern that over a period in excess of 24 hours, contaminants in the CO2 are actually absorbed into the Tedlar itself, and so when analysis is performed, the CO2 appears to be contaminant-free.

Another area which gives rise to concern is that of cross-contamination. In the CO2 distribution chain, the distributor may purchase CO2 from one or more suppliers and place the gas into a stock lank of their own. Little explanation is required to point out that the clean CO2 could become contaminated with ‘dirty’ gas. Additionally, what if the road tanker has had contaminated CO2 in it?

The Risks

Until the CO2 manufacturers improve quality control and implement stringent, on-line quality control measures, the entire packaged drinks industry is al risk. Given the sources from which the CO2 is derived, the likelihood of another ‘benzene’ scare is quite high. The analysis techniques that are employed by many of the CO2 manufacturers are at best badly flawed and it is easy to see how contaminated CO2 has entered the food chain and will invariably do so again.

Preventing Contamination — Why Mass Spectrometry?

In the first instance the onus of responsibility is on the drinks manufacturer which must perform its own analysis in order to prevent future health scares.

Mass Spectrometry has long been accepted and wisely used in speciality gas production, a good example being diving gases, where the identification of trace level contaminants is essential. A good MS system has a response time of just 30mS, making it ideal for real time measurements. Companies that are really switched on now provide dedicated process control software and, as this software is modular in design, it can be customised for individual processes.

Apart from the speed of response, the other main advantage that Mass Spectrometry offers is its flexibility. The best systems available are capable of monitoring up to 64 individual channels in real time, which means that the system is capable of monitoring multiple components such as benzene, toluene, xylene, acetates, hydrocarbons and freons. The detection level of a good MS system for such compounds is around 5ppb. The most experienced MS companies in the field also offer a thermal desorption addition, which ensures detection levels to well below lppb. Not only does this satisfy current legislative standards, it also ensures that they will be met well into the future.

A Mass Spectrometer-based system at each point on the plant would be a very expensive method of monitoring CO2 impurities, and this does not really offer a cost effective, practical solution to the problem.

The solution is to make the most effective use of the power of the MS system, and that power is the speed of analysis coupled with very low detection limits. Pipework from each sample point on the plant is fed into a central switching unit, which in turn is coupled to the MS system, which then sequentially selects each sample line, monitors the impurity levels and then performs the necessary process control operations. The sampling time on each point would be typically 30 seconds, including sample point switchover. Multiple point switching units are capable of sampling up to 64 sample points from various locations on the plant. Good sampling units have the ability to accept sample lines at various pressures, and even liquid CO2 samples if necessary, converting the liquid sample into the gas phase. Switching of the sample lines is fully automatic and sample times for various lines can be individually set.

Another feature of the most effective systems such as the GasTrace from ESS is to have different alarm levels for different points in the plant, thus ensuring that the finished drink product does not contain contamination.

The Mass Spectrometry companies that have moved away from the ‘scientific’ mentality and become switched on to process control now offer fully automated software with automatic calibration, and have direct signal links by industry standard 4-20mA or 1-5V signals, allowing easy connection to world class SCADA systems for total plant control. Software packages will store data to individual files and the data will interpret itself against either a statistical database or against the pre-set alarm conditions.

Having outlined the technology and the reasons as to how contamination in CO2 can occur, let us now turn our thoughts to real life applications and the benefits that MS offers to bottlers and packers of carbonated drinks. In order to do this, we should consider the entire distribution of the CO2 throughout every stage of the bottling process.

Immediately, we can see that incoming CO2 deliveries can be checked for contamination. Prior to replenishing the CO2 stock tank, the MS system can be connected to the road/rail tanker for analysis of the quality of the CO2. This analysis would take in the region of two to three minutes. A good system would also give an automatic printout of the analysis certificate and would give pass and fail conditions. The CO2 shipment would then be either rejected or accepted based upon the analysis results. With process control interfacing, a lock could be activated to enable/prevent the operator from filling the stock tank. Cross-contamination of clean CO2 within the stock tank could also be prevented.

If we then take this a step further, the analysis has been performed and the CO2 is declared ‘clean’ and the stock tank replenished. We then need to look at other areas where contamination can enter the system.

Most bottling plants have some sort of filtration system for the CO2 before it is admitted into the product. Usually this takes the form of a charcoal filter. Prior to this filter, the CO2 may pass through compressors, valve arrangements and pipework. A leaking seal on a compressor may cause the ingress of compressor oil into the CO2. In many cases this would be a hydrocarbon-based oil and the result would be the detection of benzene and other hydrocarbons in the finished product. If a valve seal is worn, grease from the valve may pass through the valve into the CO2, resulting in similar problems.

Pipework in plants is also an area of concern. Copper pipe is often found and oxides may form in this pipework. Also, due to the thermal properties of copper, any contaminants that were present in the CO2 would condensate onto the inner wall, thus ‘concentrating’ the contaminants.

Plastic or rubber pipework causes similar problems and can be attributed to contributing levels of styrene in the CO2. This is particularly the case in instances where the pipework is old and the plastic or rubber material has started to degrade.

The filtration system is supposed to remove these contaminants. However, the behaviour of these filters is such that they become saturated after a period of time and thus largely ineffective at ‘trapping’ contaminants. These filters usually have a regeneration facility, which has traditionally been implemented at certain time intervals. There are concerns over this approach; if the contaminant level is high, the filter will require regeneration earlier; it the gas is very clean, obviously it would be financially more viable to continue to use the filter and continue production. By monitoring the inlet and outlet of the filter continuously, its efficiency can be continuously monitored and regeneration executed as a function of this efficiency.

As far as CO2 is concerned, the final stage of its cycle through the bottling process is dispensation into the product itself. Obviously, as far as the drinks manufacturer is concerned, this is the critical stage, as this would be the final point in the production cycle where the manufacturer can take remedial action, should there be a problem. Given the volume of product that passes through a normal bottling plant, a monitoring system with an extremely fast response is required, with the capability to control or even stop the bottling process if required.

It is evident that MS offers real time monitoring for CO2 distribution throughout the bottling plants, providing excellent quality assurance in so far that the CO2 used in the bottled product is either certified clean or rejected at source. With multiple point monitoring, the exact location of a problem ‘area’ on the bottling plant (eg a compressor) would be easily and quickly identified, allowing the appropriate remedial action to be taken.

Furthermore, the legal permitted levels of contamination are set to go even lower, so investing in future proof technology is imperative. Companies who offer sub-ppb detection as either part of a standard package or as a modular upgrade should warrant more consideration.

The simple truth is that the drinks industry can ill afford another scare. Media interest in food products mean that the next ‘event’ will receive the highest profile possible, resulting in rather a large dent in consumer confidence. It is easy to prevent and eradicate this problem – the solution is continuous on-line contaminant monitoring. The benefit is the security that the bottled product is within the set limits plus minimal waste of product. Moreover, it is a small price to pay when compared to a product recall and the resulting loss of consumer confidence in that product.